1. Field of the Invention
The present invention relates to a CVD-SiC self-supporting membrane structure composed of a CVD-SiC membrane simple substance of high purity. More specifically, the invention relates to a CVD-SiC self-supporting structure which is suitable for a jig or member for the semiconductor equipment, such as a holder (plate-like, ring-like) for transfer or supporting the wafer within the semiconductor thermal treatment equipment, a liner tube, a dummy wafer, and a gas introducing tube, for example, and a method for manufacturing the same.
2. Description of the Related Art
For the semiconductor process members, a single wafer processing and the fast thermal treatment process techniques have progressed along with the larger diameter and higher integration of silicone wafers. In such a process technique, the lighter weight and lower heat capacity of members for use with the equipment are required. As one solving means, a manufacturing technique for members with a CVD self-supporting membrane structure has been examined (refer to JP-A-4-358068, JP-A-6-188306, JP-A-7-188927, and JP-A-10-12563). For example, in JP-A-7-188927, an invention was described in which the conventional CVD self-supporting membrane is weak in mechanical strength, because the crystal structure is anisotropic, and to improve this weakness, the orientation of crystal grains is randomized. Also, in JP-A-10-12563, an invention was described in which the absorption characteristics of the infrared ray are improved to enhance the temperature dependency in the thermal treatment of semiconductors. Further, in JP-A-11-121315, an invention was described in which because an optical sensor is employed in handling the process member, a plurality of layers made of silicon carbide are laid to make the member more likely to be sensed by the optical sensor.
By the way, in the conventional CVD-SiC self-supporting membrane structure, it was difficult to suppress appropriately the warp arising during the manufacture, particularly because the structure was thin, resulting in a problem of lower yield.
Also, in the wafer supporting holder, there is a need of supporting the silicon wafer of several tens grams, but in the CVD-SiC self-supporting membrane structure, the mechanical strength is insufficient, resulting in a problem of causing fracture or deterioration owing to the mechanical impact.
Further, when such CVD-SiC self-supporting membrane structure was used as a wafer supporting holder, a dummy wafer, a liner tube, or a gas introducing tube disposed within the thermal treatment equipment for semiconductor, there was a problem of causing crack or fracture in the structure, owing to the thermal shock, subjected to a heat history with high rate temperature rise or fall in making the thermal treatment of wafers.
The present invention has been achieved to solve the above-mentioned problems with the conventional art, and it is an object of the invention to improve the manufacturing yield of CVD-SiC self-supporting membranes by resolving the warp particularly after shaping the CVD-SiC self-supporting membranes, and improve the manufacturing yield of silicon devices by increasing the mechanical strength and the heat resistance to prevent fracture or particle development during the use of process members.
The present invention provides a CVD-SiC self-supporting membrane structure having a plurality of SiC layers laminated by a Chemical Vapor Deposition (CVD) method, wherein a layer A having a peak intensity (height) ratio r=xcex2(220)/xcex2(111) of xcex2(220) to xcex2(111) peak intensities of the X-ray diffracted beams in a thickness direction being 0.1 or more, and a layer B having a peak intensity ratio r of 0.01 or less are laminated alternately and repeatedly, and the layer A is laid on either side in the thickness direction.
Also, the invention provides a method for manufacturing a CVD-SiC self-supporting membrane structure, including a step I of forming a CVD-SiC membrane that is a layer A by heating a substrate easily removable by burning or chemical treatment such as a carbon substrate, a tungsten substrate or a molybdenum substrate in the atmosphere of a mixture gas having a relatively lower concentration of hydrogen containing at least dichlorosilane, ethylene, and hydrogen, and a step II of forming a CVD-SiC membrane that is a layer B using a mixture gas having a higher concentration of hydrogen than the concentration of the mixture gas. The higher or lower concentration of hydrogen indicate the levels of hydrogen with a constant concentration of the source gases comprising dichlorosilane and ethylene. That is to say, the layer A is formed under the atmosphere condition of higher concentration of the source gas whereas the layer B is formed under that of lower concentration. The method further includes repeating these steps multiple times to form a CVD-SiC laminate membrane, forming the CVD-SiC membrane that is the layer A as the outermost layer, and then removing the substrate.